The report says the lost wages "occur when individuals are forced to take unpaid leave, quit working, or reduce their work hours because they cannot access childcare or paid leave." The lost wages are not just harming American families — they also take money away from local communities and the businesses that rely on consumer spending, the report says.

The US Department of Agriculture finds that new parents spend, on average, about $70 a month for baby clothes and diapers and more than $120 a month on baby food and formula. And big-ticket items like furniture and medical expenses add up quickly. Without the guarantee of paid leave while caring for a child, many new parents are faced with the choice between economic hardship and returning to work prematurely.

A box of Pampers diapers sells for $24.99 at a grocery store in Pasadena, California. Thomson Reuters According to a 2012 report from the US Department of Labor on family and medical leave, about 15% of people who were not paid or who received partial pay while on leave turned to public assistance for help. About 60% of workers who took this leave reported it was difficult making ends meet, and almost half reported they would have taken longer leave if more pay had been available.

"Support for motherhood shouldn't be a matter of luck; it should be a matter of course," YouTube CEO Susan Wojcicki wrote in an op-ed article for The Wall Street Journal. "Paid maternity leave is good for mothers, families, and business. America should have the good sense to join nearly every other country in providing it."

Wojcicki said the rate at which new moms left Google fell by 50% when in 2007 the company increased paid maternity leave to 18 weeks from 12 weeks. "Mothers were able to take the time they needed to bond with their babies and return to their jobs feeling confident and ready," she wrote. "And it's much better for Google's bottom line — to avoid costly turnover, and to retain the valued expertise, skills, and perspective of our employees who are mothers."

Andrew Bosworth, Facebook's vice president of the 600-person ads and pages team who welcomed his son Archer Americus in November 2014, previously told Business Insider that people often feared being away and losing traction, but in his experience the opposite effect happened after returning from parental leave.

"I'm probably doing better work in less time," he says. "I hear that repeated often among my peers and among my reports, which is nice. And I think there's some value there that's hard to capture."

In 2004, California became the first state to implement a paid-family-leave policy that enables most Californians to receive 55% of their usual salary (up to $1,104 a week) for a maximum of six weeks.

Moms are more likely to return to work after taking paid maternity leave. Shutterstock According to a report from the President's Council of Economic Advisers, more than 90% of employers affected by California's paid family-leave initiative reported either positive or no noticeable effect on profitability, turnover, and morale.

The study also found these women to be 39% less likely to receive public assistance and 40% less likely to receive food stamps in the year after a child's birth compared with those who didn't take any leave.

And research out of The Institute for the Study of Labor in Bonn, Germany, indicates higher education, IQ, and income levels in adulthood for children of mothers who used maternity leave — the biggest effect comes for children from lower-educated households. The researchers cited this as a significant discussion for policymakers to have, as it could reduce the existing gap in education and income in the US.

Babies are healthier when their parents can afford to take care of them.Flickr/Nana B AgyeiThere's plenty of evidence that supports the effectiveness of paid paternity leave, too.

But research out of Israel shows the more leave men take to care for children when they're young, the more the fathers undergo changes in the brain that make them better suited to parenting. And a study by two Columbia University Social Work professors found that fathers who take two or more weeks off after their child is born are more involved in their child's care nine months later. Simply put, paid paternity leave can help foster better father-child relationships.